Method for producing a reverse osmosis membrane and reverse osmosis membrane produced thereby

Abstract

This invention relates to a method for preparing a reverse osmosis membrane and the reverse osmosis membrane prepared therefrom. The method includes the following steps: preparing a polymer solution as a casting solution, allowing the casting solution to form a polymer porous base membrane on a reinforcing material, and sequentially contacting the polymer porous base membrane with a first phase solution and a second phase solution to form a functional layer. The first phase solution contains an amine compound, a first-phase additive, and water; the second phase solution contains an acyl chloride compound, a second-phase additive, and a solvent. The first-phase additive is a hyperbranched polymer, and the second-phase additive is a halogenated heterocyclic compound. A reverse osmosis membrane is obtained after post-treatment. The reverse osmosis membrane prepared by the method of this invention exhibits both high flux and high desalination rate, and possesses excellent antifouling durability, acid wash resistance, and alkali wash resistance. The reverse osmosis membrane prepared by the method of this invention can be effectively applied to seawater desalination.

Description

Technical Field

[0001] This invention relates to the technical field of water treatment membranes, and more specifically to the technical field of reverse osmosis membranes, particularly to a method for preparing a fouling-resistant reverse osmosis membrane with high flux and high desalination rate that can be used for seawater desalination, and to a reverse osmosis membrane prepared therefrom. Background Technology

[0002] According to relevant survey data, the total volume of water on Earth is approximately 1.386 billion cubic kilometers, with seawater accounting for 97.5% of the total, while freshwater accounts for only 2.5%. Therefore, seawater desalination has gradually become an effective way to solve the global water shortage problem. Traditional seawater desalination processes mainly include distillation, multi-stage flash evaporation, and freezing methods. These processes are complex, inefficient, and energy-intensive, limiting their application in the industrial sector.

[0003] Reverse osmosis technology, as a new technology for seawater desalination, has the advantages of good treatment effect, high recovery rate, low energy consumption and low cost, and has gradually become the first choice for newly built seawater desalination plants. However, in practical applications, reverse osmosis membranes used for seawater desalination often face problems such as easy fouling of the membrane surface and poor membrane permeability (usually manifested as low water flux) due to the constraints of membrane materials and the operating environment.

[0004] Membrane fouling and poor permeability lead to high operating pressure, high energy consumption, and low desalination efficiency during seawater desalination, thus limiting the application of reverse osmosis technology. Therefore, addressing the issues of membrane fouling and low permeability is crucial for promoting the development of industrial seawater desalination reverse osmosis technology.

[0005] To address the fouling problem of reverse osmosis membranes used in seawater desalination, the industrial sector typically employs acid or alkali washing to restore membrane performance after fouling. However, prolonged or repeated acid and alkali washing significantly reduces the stability of the membrane material, leading to severe performance degradation. Therefore, it is necessary to develop membrane materials with excellent antifouling properties to fundamentally solve the problem of membrane fouling during seawater desalination.

[0006] Hydrophilic modification of membrane surfaces is an effective way to enhance their antifouling ability. The simplest and most feasible method is to coat the functional layer of the membrane with a hydrophilic layer to enhance its antifouling performance.

[0007] Patent document 1 (CN101130444A) discloses coating a membrane surface with a dense hydrophilic crosslinked polyvinyl alcohol (PVA) layer to enhance the membrane's antifouling ability. However, since the PVA layer is only bonded to the desalination layer on the membrane surface through physical action, the adhesion is poor, and the PVA layer is prone to detachment during actual operation, resulting in insufficient antifouling durability.

[0008] Patent document 2 (CN102921315A) discloses a method that introduces PVA molecules into a polyamide desalination layer, causing some of the hydroxyl groups of PVA to react with acyl chloride groups. The unreacted hydroxyl groups then participate in the formation reaction of the PVA crosslinking layer together with the hydroxyl groups on the subsequently coated PVA molecules. This allows the polyamide desalination layer and the PVA crosslinking layer to be connected through chemical bonding, improving the adhesion of the hydrophilic PVA coating layer and thus further enhancing the antifouling durability of the reverse osmosis membrane used for seawater desalination. However, a drawback of this method is that the hydrophilic PVA coating layer easily clogs the pores of the membrane separation layer, resulting in a significant decrease in the membrane's permeability performance, i.e., water flux.

[0009] Therefore, the existing reverse osmosis membranes used for seawater desalination suffer from problems such as easy fouling of the membrane material and low permeability during practical operation, which have become bottlenecks restricting the development of current seawater desalination reverse osmosis technology. Improving the selective separation and permeability performance of reverse osmosis membranes used for seawater desalination, and ensuring their anti-fouling durability, are the biggest challenges currently facing the seawater desalination application field. Summary of the Invention

[0010] The problem the invention aims to solve

[0011] In view of the above-mentioned problems in the prior art, the purpose of the present invention is to provide a method for preparing a reverse osmosis membrane and a reverse osmosis membrane prepared therefrom, which not only has high flux and high desalination rate, but also excellent anti-fouling durability, so as to be effectively used for seawater desalination.

[0012] Solutions for solving problems

[0013] Through in-depth research, the inventors of this invention believe that, considering the composition of the main seawater solution and the seawater desalination efficiency, the functional layer (also known as the separation layer or desalination layer) of the reverse osmosis membrane used for seawater desalination must possess high selective separation, excellent permeation performance, and stability of permeation performance and antifouling performance during long-term use.

[0014] The inventors of this invention have discovered that the high content of active functional groups in hyperbranched polymers can act as crosslinking sites and chemically react with acyl chloride monomers participating in interfacial polymerization to form functional layers, thereby binding them to the polymer backbone of the functional layers formed through interfacial polymerization. This improves the crosslinking degree and stability of the functional layers formed through interfacial polymerization. This invention uses hyperbranched polymers as first-phase additives contained in the first-phase solution to chemically react with acyl chloride monomers contained in the second-phase solution, thereby improving the crosslinking degree of the functional layers and ensuring a high desalination rate for reverse osmosis membranes used in seawater desalination.

[0015] The inventors of this invention have also discovered that halogen atoms in halogenated heterocyclic compounds have high reactivity and are easily controllable. By adjusting the temperature during the interfacial polymerization reaction within a suitable range, the reaction between halogen atoms and amine monomers contained in the first-phase solution can be adjusted, thereby regulating the structure and cross-linking degree of the functional layer formed through the interfacial polymerization reaction, achieving adjustment of the porosity of the functional layer, and improving the water flux of the membrane. This invention uses halogenated heterocyclic compounds as a second-phase additive contained in the second-phase solution to chemically react with amine monomers contained in the first-phase solution, thereby adjusting the porosity of the functional layer and improving the flux of the reverse osmosis membrane. Furthermore, the introduction of the heterocyclic structure also endows the functional layer with good acid and alkali cleaning resistance, improving the performance degradation problem faced by reverse osmosis membranes during acid or alkali washing to restore membrane performance after fouling, extending the service life of the reverse osmosis membrane in seawater desalination, and improving the membrane's durability.

[0016] In this invention, by using a first-phase additive and a second-phase additive, high desalination rate, high flux, acid and alkali washing resistance, and service durability of the reverse osmosis membrane can be achieved simultaneously.

[0017] Furthermore, the inventors of this invention have discovered that, in the post-treatment process, by adding an activator to the post-treatment solution and adjusting the post-treatment temperature within a suitable range, unreacted halogen atoms in halogenated heterocyclic compounds can be fully hydrolyzed, generating hydrophilic hydroxyl groups on the membrane surface, thereby improving the antifouling durability of the reverse osmosis membrane.

[0018] This invention provides a method for preparing a reverse osmosis membrane, the method comprising the following steps:

[0019] A polymer solution is prepared as a casting solution, and the casting solution is used to form a porous polymer base film on the reinforcing material;

[0020] The polymer porous membrane is sequentially contacted with a first phase solution and a second phase solution to form a functional layer. The first phase solution contains an amine compound, a first phase additive, and water. The second phase solution contains an acyl chloride compound, a second phase additive, and a solvent. The first phase additive is a hyperbranched polymer, and the second phase additive is a halogenated heterocyclic compound. The step of forming the functional layer is carried out at a temperature of 5 to 60°C.

[0021] A reverse osmosis membrane is obtained through post-treatment, wherein the post-treatment includes contact with an aqueous solution containing an activator at a temperature of 60°C to 90°C, wherein the activator is at least one selected from sodium carbonate, potassium carbonate, sodium sulfite, sodium malonate, sodium succinate, potassium succinate, sodium hydrogen oxalate, sodium dihydrogen phosphate, sodium citrate, potassium citrate, sodium lactate, sodium bicarbonate, tert-butylamine, triethylamine, and sodium oxalate.

[0022] According to the preparation method of the present invention, the polymer solution comprises a polymer and a solvent, wherein the polymer is at least one selected from polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyether ether ketone, phenazine biphenyl polyether nitrile ketone, and phenazine biphenyl polyether ketone.

[0023] According to the preparation method of the present invention, the hyperbranched polymer is at least one selected from dendritic polyamine, dendritic polyol, star polyol, star polyamine, and star heteroarm polyamine.

[0024] According to the preparation method of the present invention, the content of the first phase additive is 0.01wt% to 2wt% based on the weight of the first phase solution.

[0025] According to the preparation method of the present invention, the halogenated heterocyclic compound is a halogenated product of at least one heterocyclic compound selected from the following heterocyclic compounds: pyrazine compounds, pyridazine compounds, thiazole compounds, quinoline compounds, triazine compounds, indole compounds, purine compounds, pyrimidine compounds, and imidazole compounds.

[0026] According to the preparation method of the present invention, the content of the second phase additive is 0.02wt% to 0.5wt% based on the weight of the second phase solution.

[0027] According to the preparation method of the present invention, the content of the activator is 0.01 wt% to 0.2 wt% based on the weight of the aqueous solution containing the activator.

[0028] The present invention also provides a reverse osmosis membrane prepared by the preparation method described in the present invention.

[0029] The reverse osmosis membrane prepared by the method described in this invention can be effectively used for seawater desalination.

[0030] The effects of the invention

[0031] The method of this invention can improve the crosslinking degree and adjust the porosity of the functional layer. This method is simple to operate, requires no modification to existing equipment, and is economical and cost-effective. The reverse osmosis membrane prepared by the method of this invention not only has high water flux and extremely high desalination rate, but also excellent resistance to acid and alkali washing, service durability, and anti-fouling durability. Attached Figure Description

[0032] Figure 1 The results show a comparison of the antifouling performance of the reverse osmosis membranes of Comparative Example 1 and Example 8. Detailed Implementation

[0033] This invention relates to a method for preparing a composite reverse osmosis membrane, which includes the following steps:

[0034] A polymer solution is prepared as a casting solution, and the casting solution is used to form a porous polymer base film on the reinforcing material;

[0035] The polymer porous membrane is sequentially contacted with a first phase solution and a second phase solution to form a functional layer. The first phase solution contains an amine compound, a first phase additive, and water. The second phase solution contains an acyl chloride compound, a second phase additive, and a solvent. The first phase additive is a hyperbranched polymer, and the second phase additive is a halogenated heterocyclic compound. The step of forming the functional layer is carried out at a temperature of 5 to 60°C.

[0036] A reverse osmosis membrane is obtained through post-treatment, wherein the post-treatment includes contact with an aqueous solution containing an activator at a temperature of 60°C to 90°C, wherein the activator is at least one selected from sodium carbonate, potassium carbonate, sodium sulfite, sodium malonate, sodium succinate, potassium succinate, sodium hydrogen oxalate, sodium dihydrogen phosphate, sodium citrate, potassium citrate, sodium lactate, sodium bicarbonate, tert-butylamine, triethylamine, and sodium oxalate.

[0037] The technical concept of the preparation method of the present invention lies in the following points:

[0038] By using hyperbranched polymers as first-phase additives contained in the first-phase solution, the high content of active functional groups in the hyperbranched polymers serves as crosslinking sites. These groups react chemically with acyl chloride monomers contained in the second-phase solution that participate in the interfacial polymerization reaction to form the functional layer, thereby binding them to the polymer backbone of the functional layer formed by the interfacial polymerization reaction. This improves the crosslinking degree and stability of the functional layer formed by the interfacial polymerization reaction, thus ensuring a high desalination rate for reverse osmosis membranes used in seawater desalination.

[0039] By using halogenated heterocyclic compounds as second-phase additives contained in the second-phase solution and adjusting the temperature during the interfacial polymerization reaction within a suitable range, the chemical reaction between halogen atoms and amine monomers contained in the first-phase solution is adjusted, thereby regulating the structure and crosslinking degree of the functional layer formed by the interfacial polymerization reaction, and thus improving the flux of the reverse osmosis membrane.

[0040] In addition, the introduction of heterocyclic structures also endows the functional layer with good resistance to acid and alkali cleaning, which improves the performance degradation problem faced by reverse osmosis membranes during acid or alkali washing to restore membrane performance after fouling, extends the service life of reverse osmosis membranes in seawater desalination, and improves the durability of membranes.

[0041] By adding an activator to the post-treatment solution and adjusting the post-treatment temperature within a suitable range, the unreacted halogen atoms in the halogenated heterocyclic compounds are fully hydrolyzed, generating hydrophilic hydroxyl groups on the membrane surface, thereby improving the antifouling durability of the reverse osmosis membrane.

[0042] In the preparation method of this invention, a polymer solution is prepared as a casting solution, and the casting solution is coated onto a reinforcing material to form a polymer porous base film (also known as a polymer porous support film). Preferably, the reinforcing material is a nonwoven fabric, such as polypropylene (PP, also known as polypropylene fiber) nonwoven fabric, polyester (PET) nonwoven fabric, acrylic fiber (PAN) nonwoven fabric, and chlorofiber (PVC) nonwoven fabric. There are no particular limitations on the coating method; casting, dip coating, and blade coating methods can be used.

[0043] After the casting solution is coated onto the reinforcing material, it is then immersed in a coagulation bath, allowing the casting solution to solidify and form a polymer porous base membrane. In the preparation method of the present invention, the coagulation bath is preferably a water bath, and the temperature of the coagulation bath is not particularly limited, but is usually in the range of 10°C to 30°C.

[0044] In the preparation method of the present invention, the polymer solution comprises a polymer and a solvent, wherein the polymer is at least one selected from polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyetheretherketone, phenazine biphenyl polyether nitrile ketone, and phenazine biphenyl polyetherketone. Preferably, the concentration of the polymer is 10-30 wt% based on the weight of the polymer solution.

[0045] In the preparation method of the present invention, there is no particular limitation on the solvent contained in the polymer solution, as long as it can dissolve the polymer, such as N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), N-methyl-2-pyrrolidone, etc.

[0046] In the preparation method of the present invention, the polymer porous base membrane is sequentially contacted with a first phase solution and a second phase solution to form a functional layer. The first phase solution contains an amine compound, a first phase additive and water, and the second phase solution contains an acyl chloride compound, a second phase additive and a solvent. The first phase additive is a hyperbranched polymer and the second phase additive is a halogenated heterocyclic compound.

[0047] There is no specific limit to the contact time, which is usually between 0.5 min and 5 min.

[0048] In the preparation method of this invention, the amine compound is not limited, and amine compounds commonly used in the art for interfacial polymerization reactions can be used. Examples include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, N,N-dimethyl-m-phenylenediamine, pyromellitic triamine, piperazine, 3-aminopiperazine, 1,4-cyclohexanediamine, N,N-dimethylcyclohexanediamine, triethanolamine, diisobutylamine, n-hexylamine, decylamine, dodecaneamine, polyetheramine, etc. Preferably, the concentration of the amine compound is 0.5-5 wt% based on the weight of the first phase solution.

[0049] In the preparation method of the present invention, preferably, the hyperbranched polymer is selected from at least one of dendritic polyamine, dendritic polyol, star polyol, star polyamine, and star heteroarm polyamine.

[0050] Examples of dendritic polyamines include polyethyleneimine, polyamide-amine, polydopamine, polyethyleneimine, polyetherimide, polymethacrylamide, and polybismaleimide; examples of dendritic polyols include α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, sodium cyclodextrin sulfate, tannic acid, xylan, sorbitol, and chitosan; examples of star-shaped polyols include four-armed polyethylene glycol-alcohol, six-armed polyethylene glycol-alcohol, and eight-armed polyethylene glycol-alcohol. Examples of star-shaped polyamines include twelve-armed polyethylene glycol-alcohol, six-armed polyvinyl alcohol-amine, eight-armed polyvinyl alcohol-amine, four-armed polyimide-amine, and six-armed polyimide-amine. Examples of star-shaped hetero-armed polyamines include four-armed azo polyethylene glycol triazine-polyamide-amine, four-armed azo polyethylene glycol triazine-glycidyl ether, six-armed ethylenediamine core polydopamine-polyethyleneimine, and eight-armed ethylenediamine core polymethacrylamide-polyethyleneimine.

[0051] In the preparation method of the present invention, preferably, the content of the first phase additive is 0.01wt% to 2wt% based on the weight of the first phase solution. When the content is less than 0.01wt%, the degree of cross-linking of the functional layer is insufficient, and the desalination rate of the prepared reverse osmosis membrane is not well improved; when the content is greater than 2wt%, the first phase additive will lead to the consumption of a large amount of second phase monomer, affecting the main skeleton structure of the prepared reverse osmosis membrane and causing defects in the functional layer.

[0052] In the preparation method of the present invention, there is no limitation on the acyl chloride compound; acyl chloride compounds commonly used in the art for interfacial polymerization reactions can be used, such as trimesoyl chloride, terephthaloyl chloride, o-chlorobenzoyl chloride, and isophthaloyl chloride. Preferably, the concentration of the acyl chloride compound is 0.1-1 wt% based on the weight of the second phase solution.

[0053] In the preparation method of the present invention, the halogenated heterocyclic compound is a halogenated product of at least one heterocyclic compound selected from the following heterocyclic compounds: pyrazine compounds, pyridazine compounds, thiazole compounds, quinoline compounds, triazine compounds, indole compounds, purine compounds, pyrimidine compounds, and imidazole compounds.

[0054] Examples of halogenated pyrazine compounds include 2,3-dichloropyrazine, 2,5-dichloropyrazine, 2-chloro-3-methyl-5-bromopyrazine, 2-amino-3-chloro-6-bromopyrazine, 2,3,5-trichloropyrazine, 2,3,5,6-tetrachloropyrazine, 2-chloro-3-bromopyrazine, 2,3-dichloro-5-bromopyrazine, 2,3-dichloro-5,6-dibromopyrazine, 2-chloro-3,5,6-tribromopyrazine, and 2,3,5,6-tetrabromopyrazine; examples of halogenated pyridazine compounds include 3,4-dichloropyridazine, 5,6-dichloropyridazine, 3,4,5-trichloropyridazine, 3,5,6-trichloropyridazine, 3-chloro-5-bromopyridazine, and 3-chloro-6-bromopyridazine. Examples of halogenated thiazole compounds include 3-chloro-5,6-dibromopyridazine, 3-methyl-4-chloro-5-bromopyridazine, 3,4,5-tribromopyridazine, and 3-chloro-4-methyl-5,6-dibromopyridazine; halogenated thiazole compounds include 2,4,5-trichlorothiazole, 2,4-dichlorothiazole, 2,5-dichlorothiazole, 4,5-dichlorothiazole, 2-chloro-4,5-dibromothiazole, 2,4-dibromo-5-chlorothiazole, 2,4,5-tribromothiazole, 2-methyl-4,5-dichlorothiazole, 2,5-dibromo-4-chlorothiazole, and 4-methyl-2,5-dichlorothiazole; halogenated quinoline compounds include 2,3-dichloro-4-bromoquinoline, 3,4-dichloro-6-bromoquinoline, etc. Examples of halogenated triazine compounds include 2,3,5-trichloro-4,5-dibromoquinoline, 2-chloro-5,6-dibromoquinoline, 3,5-dichloro-6,7,8-tribromoquinoline, 2,4,6-trichloro-3,5,7-tribromoquinoline, 2,3-dimethyl-4-bromo-5-chloroquinoline, and 3,5,6-trimethyl-4-bromo-8-chloroquinoline. Examples of halogenated triazine compounds include 2,4-dichloro-1,3,5-triazine, 3,5-dichloro-1,2,4-triazine, 2,5,6-trichloro-1,3,4-triazine, and 3,5,6-trichloro-1,2,4-triazine. Examples of halogenated indole compounds include 2,3,5-trichloroindole, 4,5,6-trichloroindole, and 2- Examples of halogenated purine compounds include chloro-4-bromoindole, 2-methyl-4,6-dibromoindole, 2,5,6-trichloro-4-methylindole, 2,4-dimethyl-3,5-dichloro-7-bromoindole, and 3-chloro-5,6-dibromoindole; halogenated purine compounds include 2,6-dichloropurine, 2,8-dichloropurine, 2-chloro-6-bromopurine, 2,6,8-trichloropurine, and 2-chloro-6,8-dibromopurine; halogenated pyrimidine compounds include 2,5-dichloropyrimidine, 5,6-dichloropyrimidine, 2,5,6-trichloropyrimidine, 2-chloro-5,6-dibromopyrimidine, 2,4,6-tribromo-5-methylpyrimidine, and 2,4-dimethyl-5-chloro-6-bromopyrimidine.Examples of halogenated imidazole compounds include 2,4-dichloroimidazole, 2,5-dichloroimidazole, 2-chloro-4-bromoimidazole, 2,4,5-trichloroimidazole, 2-bromo-4,5-dichloroimidazole, 2,4-dibromo-5-bromoimidazole, and 2-methyl-4,5-dichloroimidazole.

[0055] In the preparation method of the present invention, preferably, the content of the second phase additive is 0.02wt% to 0.5wt% based on the weight of the second phase solution. When the content is less than 0.02wt%, the control over the porosity of the functional layer is insufficient, which will result in poor flux improvement of the prepared reverse osmosis membrane and insignificant improvement in antifouling performance during post-treatment. When the content is greater than 0.5wt%, it will affect the main framework structure of the functional layer, and the reduced content of acyl chloride monomers will result in a lower degree of crosslinking of the functional layer, leading to a significant reduction in the performance of the prepared reverse osmosis membrane.

[0056] In the preparation method of the present invention, the post-treatment includes contacting with an aqueous solution containing an activator. Preferably, the activator is at least one selected from sodium carbonate, potassium carbonate, sodium sulfite, sodium malonate, sodium succinate, potassium succinate, sodium hydrogen oxalate, sodium dihydrogen phosphate, sodium citrate, potassium citrate, sodium lactate, sodium bicarbonate, tert-butylamine, triethylamine, and sodium oxalate.

[0057] In the preparation method of this invention, the contact temperature between the above-mentioned agent and the aqueous solution containing the activator is between 60°C and 90°C. When the temperature is below 60°C, the unreacted halogen atoms in the halocyclic compounds are difficult to hydrolyze to form hydrophilic hydroxyl groups, which is detrimental to improving the antifouling performance of the prepared reverse osmosis membrane; when the temperature is above 90°C, the activator solution approaches boiling, affecting the control of the activation process. There is no particular limitation on the contact time, which is typically between 30 min and 180 min.

[0058] In the preparation method of the present invention, preferably, the content of the activator is 0.01 wt% to 0.2 wt% based on the weight of the aqueous solution containing the activator. When the content is less than 0.01 wt%, the concentration of the activator is too low, the activation ability is insufficient, and the unreacted halogen atoms in the halogenated heterocyclic compounds cannot be fully hydrolyzed and converted into hydrophilic hydroxyl groups, thus limiting the improvement of the antifouling performance of the prepared reverse osmosis membrane; when the content is greater than 0.2 wt%, the concentration of the activator is too high, the stability of the desalination layer structure on the surface of the prepared reverse osmosis membrane decreases, resulting in a serious degradation of the membrane performance.

[0059] In the preparation method of this invention, the step of forming the functional layer is carried out at a temperature of 5 to 60°C. When the temperature is below 5°C, the diffusion ability of the halogenated heterocyclic compounds is limited, and their reactivity is low, making it difficult to regulate the porosity of the desalination layer of the reverse osmosis membrane, resulting in poor membrane flux improvement. When the temperature is above 60°C, the halogen atoms in the structure of the halogenated heterocyclic compounds will be completely reacted, which is not conducive to the generation of hydrophilic hydroxyl groups on the surface of the reverse osmosis membrane and the improvement of the membrane's antifouling performance during the post-treatment activation process.

[0060] As a non-limiting example, the method for preparing the reverse osmosis membrane of the present invention includes the following steps:

[0061] The polymer solution is coated onto a nonwoven fabric with a scraper and then immersed in a water bath to form a porous polymer base membrane.

[0062] A first-phase solution containing hyperbranched polymers is uniformly applied to the surface of a polymer porous membrane and allowed to fully contact for 0.5–5 minutes. Excess residual solution on the surface of the polymer porous membrane is removed by an air knife. Then, a second-phase solution containing halogenated heterocyclic compounds is uniformly applied. The first-phase solution and the second-phase solution are allowed to fully contact for 0.5–5 minutes at a temperature of 5–60°C to allow interfacial polymerization to occur, generating a cross-linked structure and thus forming a functional layer.

[0063] A reverse osmosis membrane is prepared by immersing the membrane in an aqueous solution containing an activator at a temperature of 60°C to 90°C for post-treatment to generate hydrophilic hydroxyl groups on the membrane surface.

[0064] This invention also relates to a reverse osmosis membrane prepared by the method according to the invention. Preferably, the reverse osmosis membrane comprises, from bottom to top: a non-woven fabric layer, a polymer porous support layer, and a functional layer (also known as a desalination layer). The reverse osmosis membrane not only has high water flux and extremely high desalination rate, but also excellent resistance to acid and alkali washing, service durability, and anti-fouling durability, and can be effectively applied to seawater desalination.

[0065] Example

[0066] The present invention will be further described in detail below with reference to specific embodiments, but the technical solutions of the present invention are by no means limited to the following embodiments. It should be noted that, unless otherwise specified, the reagents, raw materials and equipment used in the embodiments are all commercially available conventional products.

[0067] Compare with Example 1

[0068] The polysulfone solution was directly coated onto the nonwoven fabric with a doctor blade and then immersed in a water bath to form a polysulfone porous base film.

[0069] The first phase solution was uniformly applied to the surface of the polysulfone porous membrane and allowed to contact for 3 minutes. The first phase solution consisted of 3 wt% m-phenylenediamine, 0.05 wt% sodium dodecyl sulfate, 0.02 wt% sodium hydroxide, and the remainder water. Excess residual solution was removed from the porous membrane surface using an air knife. Then, the second phase solution, consisting of 0.3 wt% trimesoyl chloride and the remainder n-hexane, was uniformly applied. The first and second phase solutions were allowed to contact for 1 minute at 20°C to obtain the reverse osmosis membrane. This membrane was then immersed in deionized water for later use.

[0070] Example 1

[0071] The polysulfone solution was directly coated onto the nonwoven fabric with a doctor blade and then immersed in a water bath to form a polysulfone porous base film.

[0072] A first-phase solution containing polydopamine was uniformly applied to the surface of a polysulfone porous membrane and allowed to contact for 3 minutes. The first-phase solution consisted of 0.15 wt% polydopamine, 3 wt% m-phenylenediamine, 0.05 wt% sodium dodecyl sulfate, 0.02 wt% sodium hydroxide, and the balance being water. Excess residual solution on the surface of the polysulfone porous membrane was removed using an air knife. Then, a second-phase solution containing 2,3,5-trichloropyrazine was uniformly applied. The second-phase solution consisted of 0.02 wt% 2,3,5-trichloropyrazine, 0.3 wt% trimesoyl chloride, and the balance being n-hexane. The first-phase solution and the second-phase solution were allowed to contact for 1 minute at 20°C to form a functional layer.

[0073] The reverse osmosis membrane was obtained by immersing it in an aqueous solution containing 0.05 wt% sodium carbonate at 80°C for 60 min after activation.

[0074] Example 2

[0075] Example 2 was carried out in the same manner as Example 1, except that 0.15 wt% polydopamine was replaced with 0.15 wt% octa-arm polyvinyl alcohol-amine, 0.02 wt% 2,3,5-trichloropyrazine was replaced with 0.02 wt% 2-bromo-4,5-dichloroimidazole, and 0.05 wt% sodium carbonate was replaced with 0.05 wt% sodium sulfite.

[0076] Example 3

[0077] Example 3 was carried out in the same manner as Example 1, except that 0.15 wt% polydopamine was replaced with 0.30 wt% α-cyclodextrin, 0.02 wt% 2,3,5-trichloropyrazine was replaced with 0.02 wt% 2-chloro-6,8-dibromopurine, and 0.05 wt% sodium carbonate was replaced with 0.05 wt% potassium oxalate.

[0078] Example 4

[0079] Example 4 was carried out in the same manner as Example 1, except that 0.15 wt% polydopamine was replaced with 0.30 wt% hexazine-ethylenediamine-polydopamine-polyethyleneimine, 0.02 wt% 2,3,5-trichloropyrazine was replaced with 0.02 wt% 3,5,6-trichloropyridazine, and 0.05 wt% sodium carbonate was replaced with 0.05 wt% sodium dihydrogen phosphate.

[0080] Example 5

[0081] Example 5 was carried out in the same manner as Example 1, except that 0.15 wt% polydopamine was replaced with 0.45 wt% polyamide-amine, 0.02 wt% 2,3,5-trichloropyrazine was replaced with 0.02 wt% 2,5,6-trichloro-1,3,4-triazine, and 0.05 wt% sodium carbonate was replaced with 0.05 wt% tert-butylamine.

[0082] Example 6

[0083] Example 6 was performed in the same manner as Example 1, except that 0.15 wt% polydopamine was replaced with 0.45 wt% polyamide-amine, 0.02 wt% 2,3,5-trichloropyrazine was replaced with 0.04 wt% 2,4,6-tribromo-5-methylpyrimidine, and 0.05 wt% sodium carbonate was replaced with 0.1 wt% triethylamine, and an activation treatment was performed at 80°C for 90 min.

[0084] Example 7

[0085] Example 7 was performed in the same manner as Example 1, except that 0.15 wt% polydopamine was replaced with 0.45 wt% polyamide-amine, 0.02 wt% 2,3,5-trichloropyrazine was replaced with 0.04 wt% 2-chloro-4,5-dibromothiazole, and 0.05 wt% sodium carbonate was replaced with 0.2 wt% potassium succinate, the first and second phase solutions were brought into full contact at 40°C for 2 min, and an activation post-treatment was performed at 90°C for 120 min.

[0086] Example 8

[0087] Example 8 was carried out in the same manner as Example 1, except that 0.15 wt% polydopamine was replaced with 0.45 wt% polyamide-amine, 0.02 wt% 2,3,5-trichloropyrazine was replaced with 0.06 wt% 2,3-dichloro-4-bromoquinoline, and 0.05 wt% sodium carbonate was replaced with 0.2 wt% sodium citrate, the first phase solution and the second phase solution were brought into full contact at 40°C for 2 min, and the activation post-treatment was carried out at 90°C for 150 min.

[0088] Testing of water flux and desalination rate (NaCl rejection rate) of reverse osmosis membranes

[0089] The reverse osmosis membranes prepared in Examples 1 to 8 were used to test water flux and desalination rate under the following operating conditions: operating pressure of 800 psi, feed water of 32000 ppm sodium chloride aqueous solution, and operating time of 30 min.

[0090] The water flux and desalination rate of the membrane are shown in Table 1 below:

[0091] Table 1

[0092] serial number <![CDATA[Water flux (L / m 2 h)]]> NaCl retention rate (%) Compare with Example 1 45.6 99.20 Example 1 53.8 99.46 Example 2 51.4 99.58 Example 3 49.6 99.63 Example 4 45.3 99.70 Example 5 40.3 99.86 Example 6 43.1 99.77 Example 7 46.8 99.72 Example 8 52.4 99.69

[0093] As shown in Table 1 above, the reverse osmosis membrane prepared by the method of the present invention has a high efficiency of up to 50 L / m³. 2 With a water flux of over h and an extremely high desalination rate, it can effectively achieve efficient desalination of seawater.

[0094] Hydrophilicity test of reverse osmosis membrane

[0095] The reverse osmosis membranes prepared in Examples 5 to 8 were used to test the water droplet contact angle on their surface. The results are listed in Table 2 below.

[0096] Table 2

[0097] serial number Water droplet contact angle (°) Example 5 48.7 Example 6 44.2 Example 7 39.4 Example 8 36.2

[0098] As can be seen from the results in Table 2, the reverse osmosis membrane prepared by the method of the present invention has excellent hydrophilicity.

[0099] Testing the antifouling performance of reverse osmosis membranes

[0100] The reverse osmosis membranes prepared in Comparative Example 1 and Example 8 were continuously fouled for 8 hours using an aqueous solution of bovine serum albumin (BSA) at a concentration of 50 ppm. Flux was tested before, during, and after fouling. The water flux was tested under the following operating conditions: operating pressure of 800 psi, feed water of an aqueous solution with a sodium chloride concentration of 32000 ppm, and operating time of 30 min. Cleaning was performed under the following operating conditions: feed water of pure water, operating pressure of 40 psi, and feed water flow rate of 8 m³ / min. 3 The water temperature is set to 25℃ and the cycle is stopped after 15 minutes to complete the cleaning process.

[0101] The results are shown in Figure 1 In the middle, by Figure 1As can be seen, before fouling treatment, the water flux of the reverse osmosis membrane prepared in Example 8 was significantly higher than that of the reverse osmosis membrane prepared in Control Example 1. During the fouling process, the water flux of both the reverse osmosis membrane prepared in Control Example 1 and the reverse osmosis membrane prepared in Example 8 decreased. After fouling and cleaning, the water flux recovery rate of the reverse osmosis membrane prepared in Example 8 was higher than 98%, essentially returning to the level before fouling. However, the water flux of the reverse osmosis membrane in Control Example 1 was significantly lower than the level before fouling after fouling and cleaning. Therefore, from Figure 1 The results show that the reverse osmosis membrane prepared according to the method of the present invention has excellent antifouling properties.

[0102] Testing the acid and alkali washing resistance of reverse osmosis membranes

[0103] The reverse osmosis membrane prepared in Example 8 was subjected to four acid washes with a hydrochloric acid concentration of 0.3 wt% and four alkaline washes with a sodium hydroxide concentration of 0.3 wt%. The acid washes and alkaline washes were performed alternately, with each wash lasting 4 hours. Each 4-hour acid wash and 4-hour alkaline wash was considered as one complete wash.

[0104] Testing: Water flux and desalination rate were tested before cleaning, after one cleaning cycle, after two cleaning cycles, after three cleaning cycles, and after four cleaning cycles. The water flux and desalination rate were tested under the following operating conditions: operating pressure 800 psi, influent aqueous solution with sodium chloride concentration of 32000 ppm, and operating time 30 min. The results are listed in Table 3 below.

[0105] Table 3

[0106] <![CDATA[Flux (L / m 2 h)]]> Desalination rate (%) initial value 51.4 99.60 1 wash 53.4 99.48 2 washes 52.8 99.60 3 cleanings 53.0 99.54 4 cleanings 53.6 99.56

[0107] As can be seen from the results in Table 3, the reverse osmosis membrane prepared by the method of the present invention has a high viscosity of up to 50 L / m before acid and alkali washing. 2 It has a water flux of over h and an extremely high desalination rate. After multiple acid and alkali washing processes, the desalination rate remains basically at the initial level, and the flux not only does not decrease but also slightly increases.

[0108] As can be seen from the results in Table 3, the reverse osmosis membrane prepared by the method of the present invention has excellent resistance to acid and alkali washing.

[0109] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the principles and spirit of the present invention should be included within the protection scope of the present invention.

[0110] Industrial availability

[0111] The method of this invention can improve the crosslinking degree and adjust the porosity of the functional layer. This method is simple to operate, requires no modification to existing equipment, and is economical and cost-effective. The reverse osmosis membrane prepared by this method not only has high water flux and extremely high desalination rate, but also excellent resistance to acid and alkali washing, durability, and anti-fouling durability, making it effectively applicable to seawater desalination.

Claims

1. A method for preparing a reverse osmosis membrane, characterized in that, Includes the following steps: A polymer solution is prepared as a casting solution, and the casting solution is used to form a porous polymer base film on the reinforcing material; The polymer porous membrane is sequentially contacted with a first-phase solution and a second-phase solution to form a functional layer. The first-phase solution contains an amine compound, a first-phase additive, and water. The second-phase solution contains an acyl chloride compound, a second-phase additive, and a solvent. The first-phase additive is a hyperbranched polymer. The hyperbranched polymer is at least one selected from dendritic polyamines, dendritic polyols, star-shaped polyols, star-shaped polyamines, and star-shaped heteroarm polyamines. The dendritic polyamine is at least one selected from polyethyleneimine, polyamide-amine, polydopamine, polyethyleneimine, polyetherimide, polymethacrylamide, and polybismaleimide. The dendritic polyol is at least one selected from α-cyclodextrin, β-cyclodextrin, γ-cyclodextrin, sodium cyclodextrin sulfate, tannic acid, xylan, sorbitol, and chitosan. The star-shaped polyol is at least one selected from four-arm polyethylene glycol-alcohol, six-arm polyethylene glycol-alcohol, eight-arm polyethylene glycol-alcohol, and dodecyl polyethylene glycol-alcohol. The star-shaped polyamine is selected from at least one of the following: a tetra-armed polyvinyl alcohol-amine, a hexa-armed polyvinyl alcohol-amine, an octa-armed polyvinyl alcohol-amine, a tetra-armed polyimide-amine, and a hexa-armed polyimide-amine; the star-shaped hetero-armed polyamine is selected from at least one of the following: a tetra-armed azopolyethylenediamine triazine-polyamide-amine, a tetra-armed azopolyethylenediamine triazine-glycidyl ether, a hexa-armed ethylenediamine core polydopamine-polyethyleneimine, and an octa-armed ethylenediamine core polymethacrylamide-polyethyleneimine; the second phase additive is a halogenated heterocyclic compound, which is a halogenated product of at least one heterocyclic compound selected from the following heterocyclic compounds: pyrazine compounds, pyridazine compounds, thiazole compounds, quinoline compounds, triazine compounds, indole compounds, purine compounds, pyrimidine compounds, and imidazole compounds; the step of forming the functional layer is carried out at a temperature of 5 to 60°C. A reverse osmosis membrane is obtained through post-treatment, wherein the post-treatment includes contact with an aqueous solution containing an activator at a temperature of 60°C to 90°C, wherein the activator is at least one selected from sodium carbonate, potassium carbonate, sodium sulfite, sodium malonate, sodium succinate, potassium succinate, sodium hydrogen oxalate, sodium dihydrogen phosphate, sodium citrate, potassium citrate, sodium lactate, sodium bicarbonate, tert-butylamine, triethylamine, and sodium oxalate.

2. The preparation method according to claim 1, wherein, The polymer solution comprises a polymer and a solvent, wherein the polymer is at least one selected from polysulfone, polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, polyether ether ketone, naphthalene-biphenyl polyether nitrile ketone, and naphthalene-biphenyl polyether ketone.

3. The preparation method according to claim 1 or 2, wherein, The hyperbranched polymer is selected from at least one of polydopamine, octagonal polyvinyl alcohol-amine, α-cyclodextrin, hexagonal ethylenediamine nucleopolydopamine-polyethyleneimine, and polyamide-amine.

4. The preparation method according to claim 1 or 2, wherein, The content of the first phase additive is 0.01 wt% to 2 wt% based on the weight of the first phase solution.

5. The preparation method according to claim 1 or 2, wherein, The halogenated pyrazine compounds are selected from at least one of 2,3-dichloropyrazine, 2,5-dichloropyrazine, 2-chloro-3-methyl-5-bromopyrazine, 2-amino-3-chloro-6-bromopyrazine, 2,3,5-trichloropyrazine, 2,3,5,6-tetrachloropyrazine, 2-chloro-3-bromopyrazine, 2,3-dichloro-5-bromopyrazine, 2,3-dichloro-5,6-dibromopyrazine, 2-chloro-3,5,6-tribromopyrazine, and 2,3,5,6-tetrabromopyrazine; the halogenated pyridazine compounds are selected from 3,4-dichloropyridazine, 5,6-dichloropyridazine, 3,4,5-trichloropyridazine, 3,5,6-trichloropyridazine, 3-chloro-5-bromopyridazine, 3-chloro-6-bromopyridazine, and 3-chloro- 5,6-Dibromopyridazine, 3-methyl-4-chloro-5-bromopyridazine, 3,4,5-tribromopyridazine, 3-chloro-4-methyl-5,6-dibromopyridazine; the halogenated thiazole compound is selected from at least one of 2,4,5-trichlorothiazole, 2,4-dichlorothiazole, 2,5-dichlorothiazole, 4,5-dichlorothiazole, 2-chloro-4,5-dibromothiazole, 2,4-dibromo-5-chlorothiazole, 2,4,5-tribromothiazole, 2-methyl-4,5-dichlorothiazole, 2,5-dibromo-4-chlorothiazole, 4-methyl-2,5-dichlorothiazole; the halogenated quinoline compound is selected from at least one of 2,3-dichloro-4-bromoquinoline, 3,4-dichloro-6-bromoquinoline, 2,3, 5-Trichloro-4,5-dibromoquinoline, 2-chloro-5,6-dibromoquinoline, 3,5-dichloro-6,7,8-tribromoquinoline, 2,4,6-trichloro-3,5,7-tribromoquinoline, 2,3-dimethyl-4-bromo-5-chloroquinoline, and 3,5,6-trimethyl-4-bromo-8-chloroquinoline; the halogenated triazine compound is at least one selected from 2,4-dichloro-1,3,5-triazine, 3,5-dichloro-1,2,4-triazine, 2,5,6-trichloro-1,3,4-triazine, and 3,5,6-trichloro-1,2,4-triazine; the halogenated indole compound is at least one selected from 2,3,5-trichloroindole, 4,5,6-trichloroindole, and 2-chloro-4- The compound is selected from at least one of bromoindole, 2-methyl-4,6-dibromoindole, 2,5,6-trichloro-4-methylindole, 2,4-dimethyl-3,5-dichloro-7-bromoindole, and 3-chloro-5,6-dibromoindole; the halogenated purine compound is selected from at least one of 2,6-dichloropurine, 2,8-dichloropurine, 2-chloro-6-bromopurine, 2,6,8-trichloropurine, and 2-chloro-6,8-dibromopurine; the halogenated pyrimidine compound is selected from at least one of 2,5-dichloropyrimidine, 5,6-dichloropyrimidine, 2,5,6-trichloropyrimidine, 2-chloro-5,6-dibromopyrimidine, 2,4,6-tribromo-5-methylpyrimidine, and 2,4-dimethyl-5-chloro-6-bromopyrimidine.The halogenated imidazole compounds are selected from at least one of 2,4-dichloroimidazole, 2,5-dichloroimidazole, 2-chloro-4-bromoimidazole, 2,4,5-trichloroimidazole, 2-bromo-4,5-dichloroimidazole, 2,4-dibromo-5-bromoimidazole, and 2-methyl-4,5-dichloroimidazole.

6. The preparation method according to claim 1 or 2, wherein the halogenated heterocyclic compound is at least one selected from 2,3,5-trichloropyrazine, 2-bromo-4,5-dichloroimidazole, 2-chloro-6,8-dibromopurine, 3,5,6-trichloropyridazine, 2,5,6-trichloro-1,3,4-triazine, 2,4,6-tribromo-5-methylpyrimidine, 2-chloro-4,5-dibromothiazole, and 2,3-dichloro-4-bromoquinoline.

7. The preparation method according to claim 1 or 2, wherein, The content of the second phase additive is 0.02 wt% to 0.5 wt% based on the weight of the second phase solution.

8. The preparation method according to claim 1 or 2, wherein, The content of the activator is 0.01 wt% to 0.2 wt% based on the weight of the aqueous solution containing the activator.

9. A reverse osmosis membrane prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the reverse osmosis membrane according to claim 9 in seawater desalination.

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